Energy transport in random, noisy environments plays an important role in  many areas of physics including conducting polymers and thin films.   In one dimension, it is well known that any amount of disorder leads  to localization of the eigenstates.  In such a system, the diffusion of  an initial excitation in the chain proceeds ballistically until  the localization length of the chain is reached and the transport   stops. Coupling of the disordered system to the environment, however,  is sufficient to overcome the localization, allowing for diffusive  transport in the long time limit. For large coupling, any coherences  are quickly destroyed and the diffusion proceeds by way of classical  hopping between sites. In the opposite regime of weak coupling, the  exact eigenstates of the system are given approximately by those of  the system Hamiltonian. Here the rates are accurately determined by  Fermi's golden rule and the transport proceeds via hopping  through the eigenstates. Through exact  numerical calculations, we show that these two limiting behaviors lead to a maximum in the diffusion coefficient in the intermediate coupling regime.

Exciton diffusion in 1D chains with static disorder and dynamic noise

244th National Meeting (2012)

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